Add toString() to HunkHeader

Since FileHeader provides toString() method (via DiffEntry) we could add
a similar method to HunkHeader.

Change-Id: I7886e5b8f775fa8e8478ac5af37d90b6ef677d8b

org.eclipse.jgit/src/org/eclipse/jgit/patch/HunkHeader.java

@@ -401,4 +401,17 @@ public class HunkHeader {
 		final int end = s.indexOf('\n', offsets[fileIdx]);
 		offsets[fileIdx] = end < 0 ? s.length() : end + 1;
 	}
+
+	@Override
+	public String toString() {
+		StringBuilder buf = new StringBuilder();
+		buf.append("HunkHeader[");
+		buf.append(getOldImage().getStartLine());
+		buf.append(',');
+		buf.append(getOldImage().getLineCount());
+		buf.append("->");
+		buf.append(getNewStartLine()).append(',').append(getNewLineCount());
+		buf.append(']');
+		return buf.toString();
+	}
 }